Editing Area rule (section)

===United States===
[[Wallace D. Hayes]], a pioneer of [[supersonic]] flight, developed the transonic area rule in publications beginning in 1947 with his Ph.D. thesis at the [[California Institute of Technology]].<ref name="Wallace Hayes">{{Citation | url = http://www.princeton.edu/pr/news/01/q1/0308-hayes.htm | title = Wallace Hayes | type = obituary | publisher = Princeton}}.</ref>

[[Image:Richard Whitcomb Examines Model - GPN-2000-001262.jpg|thumb|April 1955: Whitcomb examines a model aircraft designed in accordance with his area rule.]]
[[Richard T. Whitcomb]], after whom the rule is named, independently discovered this rule in 1952, while working at the [[National Advisory Committee for Aeronautics]] (NACA). While using the new Eight-Foot High-Speed Tunnel, a [[wind tunnel]] with performance up to Mach 0.95 at NACA's [[Langley Research Center]], he was surprised by the increase in drag due to shock wave formation. Whitcomb realized that, for analytical purposes, an airplane could be reduced to a streamlined body of revolution, elongated as much as possible to mitigate abrupt discontinuities and, hence, equally abrupt drag rise.<ref name=NTRS>{{cite web|last=Hallion|first=Richard P.|title=The NACA, NASA, and the Supersonic-Hypersonic Frontier|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100025896_2010028361.pdf|work=NASA|publisher=NASA Technical Reports Server|access-date=8 September 2011}}</ref> The shocks could be seen using [[Schlieren photography]], but the reason they were being created at speeds far below the speed of sound, sometimes as low as Mach 0.70, remained a mystery.

In late 1951, the lab hosted a talk by [[Adolf Busemann]], a famous German aerodynamicist who had moved to Langley after [[World War II]]. He talked about the behavior of airflow around an airplane as its speed approached the critical Mach number, when air no longer behaved as an incompressible fluid. Whereas engineers were used to thinking of air flowing smoothly around the body of the aircraft, at high speeds it simply did not have time to "get out of the way", and instead started to flow as if it were rigid pipes of flow, a concept Busemann referred to as "streampipes", as opposed to [[Streamlines, streaklines, and pathlines|streamlines]], and jokingly suggested that engineers had to consider themselves "pipefitters".

Several days later Whitcomb had a "[[Eureka (word)|Eureka]]" moment. The reason for the high drag was that the "pipes" of air were interfering with each other in three dimensions. One does not simply consider the air flowing over a 2D cross-section of the aircraft as others could in the past; now they also had to consider the air to the "sides" of the aircraft which would also interact with these streampipes. Whitcomb realized that the shaping had to apply to the aircraft ''as a whole'', rather than just to the fuselage. That meant that the extra cross-sectional area of the wings and tail had to be accounted for in the overall shaping, and that the fuselage should actually be narrowed where they meet to more closely match the ideal.